StarDate Podcast

The number of known “exoplanets” that might sustain life keeps going up – it’s in the hundreds. Such a planet is in the “habitable zone” of its parent star – the distance where conditions are most comfortable for life. That zone depends on the type of star. It’s close in for small, faint stars, but a long way out for stars that are big and bright. In fact, such stars might not even have a habitable zone. And if they do, it won’t last long. One example is Antares, the heart of the scorpion, which huddles close to the Moon tonight. Antares consists of two stars. The star we see is many times bigger and heavier than the Sun. And it’s probably 50,000 to a hundred thousand times brighter than the Sun or more. For a planet to receive the same amount of energy that Earth gets from the Sun, it would have to be at least 225 times farther out than Earth is. And at that distance, the second star in the system might make the planet’s orbit unstable. It might even kick the planet out of the system. Even if a planet did exist in the habitable zone, it wouldn’t last long. Antares is likely to explode in the next million years or so – a bad development for any planet. So if anything inhabits the Antares system, it’s probably just visiting – perhaps some scientists from another star system watching this impressive but unfriendly pair of stars. Script by Damond Benningfield

Mars appears to have a shadow this evening – a faint star with one of the more lyrical names in the heavens: Zavijava. Mars looks like a fairly bright orange star, quite low in the west as darkness falls. Zavijava is almost touching it. It’s a good bit fainter than Mars, though, so you might want to use binoculars to enhance the view. Zavijava is a pretty close neighbor. According to the Gaia space telescope, it’s just 35.88 light-years away. Only a few dozen stars that are visible to the unaided eye are closer. The star’s name comes from an Arabic phrase that means “corner of the barking dog.” But Zavijava isn’t related to any of the dogs in the night sky. Instead, it’s one of the brighter stars of the constellation Virgo, so it’s also known as Beta Virginis. Zavijava is a little bit bigger and heavier than the Sun. It’s younger than the Sun by roughly one-and-a-half billion years. But because of its greater heft, it’s already nearing the end of the main phase of life. Before long – on the astronomical timescale – it’ll undergo a series of changes in its core. That will make the star much bigger and brighter. It will remain in that phase for hundreds of millions of years. Over the past few decades, astronomers have reported the discovery of several possible planets around the star. None of those reports has stood up. But the search continues – for worlds orbiting Zavijava. Script by Damond Benningfield

For a star, passing too close to a black hole is never a good thing. If the star doesn’t get eaten, it can get kicked into a high-speed jaunt across the cosmos. And astronomers can track the path of such a star back to its birthplace. One such high-speed star is plowing through the galaxy at more than a million miles per hour. Today, it appears near the twins of Gemini. But it may have been born halfway across the sky, in Pegasus. When astronomers traced the star’s path, they found that it intersected with the star cluster Messier 15 about 20 million years ago. The star is the same age as the stars in the cluster, and it has the same composition. That suggests the star was born in M15, then booted out – probably by an encounter with a black hole more than a hundred times the mass of the Sun. Other astronomers had reported the possibility of such a black hole more than 20 years ago. And the high-speed star appears to confirm it. Originally, the star would have been a member of a binary. But the two stars passed close to the black hole – closer than Earth is from the Sun. In a complex gravitational dance, the binary was ripped apart. One star was gobbled up by the black hole. But the other one got away – beginning a high-speed dash across the galaxy. Today, the star is more than 37,000 light-years from the cluster – a possible survivor of a close encounter with a black hole. Script by Damond Benningfield

A small star with a planetary companion appears to be making a high-speed exit from the center of the Milky Way – perhaps fast enough to escape the galaxy entirely. The system is more than 24,000 light-years away, in Sagittarius. It appears to contain a red-dwarf star – a cool, faint ember about 20 percent the mass of the Sun. It’s accompanied by a “super-Neptune” – a planet about 30 times the mass of Earth. They’re separated by less than the distance from Earth to the Sun. What makes the system especially interesting is its high speed – at least 1.2 million miles per hour. That’s not fast enough to leave the Milky Way behind. But it could be moving a good bit faster. The system might have started as a member of a binary – two stars bound by gravity. The stars passed too close to the monster black hole in the galaxy’s heart. The black hole grabbed the other star, and gave the escapee a giant kick. On the other hand, the kick could have come from an encounter with a smaller black hole in the Milky Way’s crowded center. How the star maintained its grip on the planet is a key question. But the planet must have been in a tight orbit to avoid being yanked away. Researchers were scheduled to take some follow-up observations this month. That might reveal whether the system really is a star and planet on a high-speed ride through the galaxy. We’ll talk about another possible escapee tomorrow. Script by Damond Benningfield

The supermassive black hole at the heart of the Milky Way is never quiet – it’s constantly popping off. The black hole is more than four million times the mass of the Sun. It grabs passing gas clouds, asteroids, and other objects. It also sponges up gas from the “winds” produced by nearby stars. This forms a swirling disk around the black hole. As material spirals inward, it gets extremely hot. Astronomers watched the black hole with James Webb Space Telescope. They found that it produces several bright outbursts every day, with each one lasting an hour or longer. Between these outbursts there were fainter flares that usually lasted less than a minute. The flares may have different causes. Shorter flares may be caused by turbulence in the disk, which squeezes and heats pockets of gas. Particles bounce around inside these pockets, heating up and producing outbursts of energy. The longer flares may explode when magnetic fields twist together, then snap. That produces big outbursts of particles and energy like the giant flares on the Sun. The astronomers hope to take an even longer look at the system, helping them learn more about the constant flare-ups from the Milky Way’s monster black hole. The black hole is in Sagittarius. The constellation is in the south on summer evenings, and forms the outline of a teapot. The black hole is immersed in the “steam” above the spout – 26,000 light-years away. Script by Damond Benningfield

Sagittarius marks the center of our home galaxy, the Milky Way. So the constellation is packed with stars, star clouds, and star clusters. But one of the clusters doesn’t belong to the Milky Way at all – at least not yet. It’s in a small, puffy galaxy on the far edge of the Milky Way’s disk. Messier 54 is a globular cluster – a ball-shaped region about 150 light-years across, packed with hundreds of thousands of stars. Native globulars are among the Milky Way’s oldest residents – they were born with the galaxy itself. But a few of the clusters were born in other galaxies, then absorbed when their home galaxies were absorbed by the Milky Way. For a long time, astronomers thought that M54 was a charter member of the Milky Way – one of its early globular clusters. A couple of decades ago, though, they found that it’s near the center of a newly discovered galaxy, the Sagittarius Dwarf. That puts it outside the Milky Way’s disk. But the Milky Way is pulling the smaller galaxy in. Eventually, it will incorporate all of the galaxy’s stars. So M54 will become a member of the Milky Way – one of its newest residents – and one of its oldest. Sagittarius scoots low across the south on summer nights. It looks like the outline of a teapot. M54 is at the lower left corner of the teapot, but you need a telescope to see it. Script by Damond Benningfield

Mars won’t exactly roll out the red carpet for human explorers. In fact, the Red Planet could be deadly. It’s bitterly cold, the air is too thin to breathe, there’s no ozone layer to block the Sun’s ultraviolet rays, and there’s no magnetic field to deflect solar storms. And if that’s not enough, there’s one more potential hazard: dust. A recent study said the dust could damage lungs and other organs and cause nasty diseases. Dust covers much of the planet, giving Mars its orange color. It’s easily lofted by the wind, and dust storms can blanket much or all of the planet. Researchers studied the dust, along with problems that Apollo astronauts experienced with Moon dust. They found that the Mars dust grains are too small to be filtered out by the lungs. Instead, they’d enter a person’s bloodstream. Not only are the grains abrasive, but the dust contains high levels of some nasty compounds. So the dust could cause everything from thyroid problems to a condition similar to black-lung disease. Some ailments could be treated on Mars. But any serious problems might require help from Earth – a journey of months. So Mars travelers will need good air filters, self-cleaning spacesuits, and other methods to protect them from the deadly sands of Mars. Mars stands close to the crescent Moon as darkness falls this evening. It looks like a fairly bright star – a hazardous destination for human explorers. Script by Damond Benningfield

Astronomers generally don’t play many official practical jokes. But an Italian astronomer played one more than two centuries ago. And the joke is still there for everyone to see. It’s in Delphinus, the dolphin. The constellation is small and fairly dim. But five of its stars form an outline that really does resemble a dolphin, making it easy to find. It’s a third of the way up the eastern sky at nightfall, with the dolphin’s tail on the right and its snout on the left. The brightest members of the outline are Beta and Alpha Delphini. Beta is a binary – two stars bound by their mutual gravitational pull. Both are bigger, brighter, and heavier than the Sun. Alpha consists of three stars. All of them are more impressive than the Sun, with the main star almost four times the mass of the Sun. The stars also have proper names. Beta is known as Rotanev; Alpha is called Sualocin. And that’s where the joke comes in. The names first appeared in 1814, in an atlas published by the director of the Palermo Observatory. The names caught on, but their origin was a mystery. It was solved by a British astronomer 45 years later. He realized that the observatory’s assistant director at the time was Niccolo Cacciatori. In English, the name would be Nicholas Hunter; in Latin, Nicolaus Venator. Spell the Latin names backwards, and you come up with Sualocin and Rotanev – a little joke among the stars of the dolphin. Script by Damond Benningfield

Zeta Tauri is the kind of star that few of us really notice. It’s at the tip of one of the horns of Taurus, the bull. But it shines at only third magnitude. That’s no problem under dark skies, but tough to see from a light-polluted city. It’ll be much easier to find before dawn tomorrow, though, because it’ll stand just a whisker from Venus, the brilliant “morning star.” Zeta Tauri is actually two stars, not one. They’re separated by a bit more than the distance from Earth to the Sun. But at the system’s distance of about 440 light-years from Earth, it’s impossible to see them as individual stars, even with the largest of telescopes. In fact, it’s tough to even learn the nature of the two stars. One of the stars is easy to figure out. It’s about 11 times the mass of the Sun, five times wider than the Sun, and thousands of times brighter. But its companion isn’t fully understood. It may be a white dwarf – a stellar corpse as heavy as the Sun. The main star is blowing a strong wind of gas into space. That’s formed a cloud around the star. The white dwarf may pull in some of that material. As it piles up on the white dwarf it gets much hotter, making the system a strong source of X-rays. In the next few million years, the heavier star of Zeta Tauri is likely to explode as a supernova. That’ll make it impossible to overlook this currently meager star. Script by Damond Benningfield

Water, water everywhere, nor any drop to drink. The line from “The Rime of the Ancient Mariner” is true not only on Earth, but across the solar system. Water is everywhere. But it’s not in a form you could drink. It’s in the clouds of the giant outer planets, frozen in the surfaces and ice caps of planets and moons, or buried far below their surfaces. One example is Pluto. The dwarf planet is billions of miles from the Sun, so its surface is frozen. But there’s evidence that liquid water lurks far below. In fact, there could be a global ocean up to a hundred miles deep. One bit of evidence is a feature called Sputnik Planitia – a fairly smooth plain about 600 miles across. It’s almost pure white. And there are no impact craters, suggesting that the surface is young. Among its features are floating blocks of frozen gases. They resemble slabs of ice in the polar regions of Earth. That suggests they could be floating atop liquid water. Plumes of water flow upward, freezing and pushing older ice outward. In fact, the feature might have formed when a big asteroid slammed into Pluto. It vaporized the surface, exposing the ocean below. The water quickly froze, forming the plain we see today. Pluto lines up opposite the Sun this week. It’s in view all night, and shines brightest for the whole year. Script by Damond Benningfield

The east coast of Florida first heard the roar of a rocket heading toward space 75 years ago today. It failed. But it set the stage for thousands more launches – payloads intended for Earth orbit, the Moon, and targets throughout the solar system. The military had been conducting test flights from White Sands, New Mexico. But it was limited by the land-locked site. So it turned to a piece of scrubland known as Cape Canaveral. The site was chosen because it was isolated, it offered a moderate climate, and it was close to the equator, so it gave east-bound rockets an extra kick. Most important, it offered tens of thousands of square miles of open ocean to catch falling rockets. So workers carved out some space and built several launch pads. And on July 24th of 1950, they put one of them to work, launching a rocket called Bumper 8. The first stage was a V-2 captured from Germany at the end of World War II. The second stage was a small American-built rocket. As often happened in the early days, something went wrong. The rocket followed the wrong path, causing the second stage to fail. A second Bumper launch, nine days later, fared a bit better, but still didn’t achieve all of its goals. Today, Cape Canaveral and the adjoining Kennedy Space Center are busier than ever. Last year, they hosted a record 93 launches – adding to the tally of a 75-year-old spaceport. Script by Damond Benningfield

A big storm on the Sun in May of 2024 caused big trouble for satellites. And they could face even bigger troubles in the coming decades. The storm was an especially powerful outburst of energy and particles. When the storm hit Earth, it heated the outer atmosphere, causing it to expand. That increased the drag on satellites in low orbit, causing them to lose altitude. A study put the average drop at about 600 feet per day – the length of two football fields. The satellites had to fire their thrusters to stay where they belonged. The study said that thousands of satellites had to execute those maneuvers – up to 5,000 per day. It was impossible to calculate all those maneuvers at once, so the risk of collisions went way up. No impacts were reported. But the number of satellites continues to skyrocket. And another study forecasts that the Sun should get even stormier over the next 40 years or so. The Sun goes through an 11-year cycle of magnetic activity. But there’s also a cycle of cycles. The average level of activity goes down for four or five cycles, then goes up for the next four or five. The study says we’ve reached the bottom of that “super” cycle, and should be on the way up. That means more big storms from the Sun, and more maneuvering by satellites – increasing the risk of collisions in low Earth orbit. Script by Damond Benningfield

Jupiter’s Great Red Spot is one of the most intriguing features in the solar system. It’s a storm that’s big enough to swallow Earth – but getting smaller. Winds at its perimeter blow much faster than any hurricane on Earth. And it has a bright reddish orange color. Despite a century and a half of study, though, it’s still mysterious. Scientists don’t know why it’s red, why it’s getting smaller, or how it fired up in the first place. They do know that the storm drifts westward around the planet. And a recent study found that it “inches” along like a garden slug. Scientists monitored the storm for three months with Hubble Space Telescope. They already knew that the Great Red Spot goes through a 90-day cycle. But this was the first time they plotted the changes in detail. The images revealed that the spot stretches and squeezes as it moves. When it’s moving slowest, it’s stretched out. When it’s moving fastest, it’s more compressed, so it’s a little rounder. The storm’s width varies by about a hundred miles, and its height by a bit more. The spot’s average width is more than 8,000 miles. That’s only a third the size when it was first seen. No one knows whether it will continue to shrink – and eventually disappear. Look for Jupiter close to the right of the Moon in tomorrow’s dawn twilight. It looks like a bright star. But it’s so low that you need a clear horizon to spot it. Script by Damond Benningfield

The three brightest objects in the night sky team up during the early morning twilight tomorrow: the Moon and the planets Venus and Jupiter. Venus is the “morning star,” to the upper right of the Moon. Slightly fainter Jupiter is to the lower left of the Moon. It’s quite low, so you need a clear horizon to spot it. Venus and Jupiter are siblings – they were born from the same disk of material around the newborn Sun. So were Earth and the solar system’s other planets. Besides their parentage, though, Venus and Jupiter don’t have a lot in common. Venus is a ball of rock a little smaller than Earth. It’s topped by clouds of sulfuric acid. They reflect most of the sunlight that strikes them, which is one reason Venus is so bright. Another is its proximity: Venus is the second planet from the Sun, while Earth is the third. So Venus passes closer to us than any other planet. Because Venus and Earth formed so close to the Sun, they’re made mainly of rock and metal. The young Sun blew away most of the lighter materials – gas and ice. So Venus is dense and heavy. Jupiter formed much farther from the Sun, where it was much colder. It built a big core of heavy materials, then swept up a lot of gas, dust, and ice. It became the largest planet in the solar system – a dozen times the diameter of Venus, and almost 400 times its mass – the “big brother” to the rest of the planets. More tomorrow. Script by Damond Benningfield

Since the start of the Space Age, we’ve learned a lot about the other planets of the solar system. But perhaps we’ve learned the most about Venus. That’s a bit of a surprise when you consider that Venus passes closer to Earth than any other planet. Venus is the brilliant “morning star.” It lines up close to the crescent Moon before dawn the next couple of days. Venus looks so bright in part because it’s blanketed by clouds that hide the surface. And that’s the main reason we’ve had so much to learn about the planet. Without any landmarks to go by, astronomers couldn’t even tell the length of the planet’s day. They didn’t figure it out until the early 1960s. They used radio telescopes to bounce waves off the surface. The echoes revealed that a day on Venus lasts 243 Earth days. For a long time, scientists thought the clouds were made of water vapor, just like the clouds on Earth. That led to speculation that Venus was warm and wet, with giant oceans and dense jungles. Instead, the clouds are made of sulfuric acid. And they hide a surface that’s hot enough to melt lead, with not a drop of water. Today, planetary scientists are still learning about Venus. It appears to be volcanically active, for example – perhaps one of the most active worlds in the solar system. So, many more surprises could lurk below the clouds of our brilliant neighbor. Script by Damond Benningfield

The Moon and the Seven Sisters huddle up in the wee hours of tomorrow morning. The Moon will “occult” the sisters – the brightest stars of the Pleiades star cluster. The stars form a tiny dipper that marks the shoulder of Taurus, the bull. Occultations have been useful scientific tools. The way a star vanishes, then reappears, can reveal details about both the star and the Moon. If the star fades in steps, that probably means it’s a binary – two stars that orbit each other. The Moon covers up one star a moment before it hides the second one. Several binary systems were discovered this way. Watching an occultation at different wavelengths also reveals details about the individual stars, such as their brightness and temperature. Occultations also have helped map the lunar surface. The Moon isn’t smooth – it’s marked by rugged impact craters, canyons, and mountains. The precise timing of the occultation reveals whether the star was blocked by one of these features. Occultations aren’t quite as important to scientists as they once were. But they’re still interesting to watch – as the Moon “hides” a star. This occultation will be in good view from the central and western parts of the United States, although it occurs a little late for most of the eastern part of the country. The exact timing depends on your location Script by Damond Benningfield

There are several ways to envision the celestial scorpion. The main way is to look for the outline of the scorpion, which is low in the south at nightfall at this time of year. Its curving body really does resemble the nasty little arachnids. Its head is to the upper right of the body, the tail and stinger to the lower left, with the bright orange star Antares between them. Then there’s the scientific way. Astronomers have divided the sky into 88 official constellations, including Scorpius. Each one has precisely defined borders. Scorpius, for example, is bounded by 18 facets. So the constellation looks a bit like an off-center tower of boxes. Finally, there’s the astrological way – the sign of Scorpio. It’s one of the signs of the zodiac – sections of the Sun’s path across the sky. About 2500 years ago, the astrologers of ancient Babylon split the zodiac into 12 signs, all of the same width. So the Sun spent roughly the same amount of time in each sign. It was “in” Scorpio from about October 23rd to November 21st. And at the time, that was a fairly close match to the physical pattern of the scorpion. Over the centuries, though, the dates at which the Sun appears in front of a given star pattern have changed. Today, the Sun enters Scorpius several weeks later than it did centuries ago. But the astrological signs have remained fixed – away from the constellations for which they’re named. Script by Damond Benningfield

Astronauts and cosmonauts have been sharing time in orbit for three decades. But their first mission together began much earlier, with the Apollo-Soyuz Test Project. An Apollo spacecraft linked up with a Soviet Soyuz capsule in 1975. The craft had launched on July 15th. First up were two cosmonauts aboard the Soyuz, followed by three astronauts aboard the final Apollo. And 50 years ago today, the two spacecraft came together. Cosmonaut Alexei Leonov congratulated astronaut Tom Stafford, who’d flown the docking. LEONOV: Well done, Tom. It was a good show! The space travelers stayed together for two days. They shook hands, conducted some maneuvers, did some experiments, and took part in a lot of ceremonies, including a phone call from President Gerald Ford. FORD: Your flight is a momentous event and a very great achievement, not only for the five of you, but also for the thousands of American and Soviet scientists and technicians who have worked together to ensure the success of this very historic and very successful experiment in international cooperation. It took years to get the next joint mission off the ground. But today, despite wars, upheavals, and political chaos, American astronauts and Russian cosmonauts continue to meet in space. Script by Damond Benningfield

An astronomical trio lines up low in the east at first light tomorrow. Two of its members are easy to pick out: Venus, the brilliant “morning star,” with the true star Aldebaran close to its right. But to see the third member, you need to pull out your binoculars. NGC 1647 is just to the right of Venus, much closer than Aldebaran is. It’s a star cluster – a tightly packed family of hundreds of stars. Most of the cluster’s details are a bit fuzzy, though. Estimates of its age, distance, and the number of stars vary by quite a bit. In part, that’s because the cluster is behind a cloud of dust, which absorbs some of its light. But it’s also because NGC 1647 hasn’t received a lot of attention. Measurements put the cluster’s distance at about 1800 to 2,000 light-years. One study said the cluster has at least 600 member stars, while another puts the number at 1300 or more. And estimates of its age range from about 120 million years to more than 260 million. Based on the structure of NGC 1647, it appears that no matter how old it is, it may not last much longer. The cluster may be losing its grip on the stars outside its dense core. The stars are being pulled away by the gravitational tug of the rest of the galaxy. Soon, many of them could drift away – leaving a much smaller family of stars. Tomorrow: shaking hands. Script by Damond Benningfield

If you ever find yourself floating above the clouds of Saturn, gazing upon the planet’s magnificent rings, you might feel like you need to get your eyes checked. Even at noon, when the Sun is highest in the sky, the view will look as dim as the minutes before sunrise or after sunset here on Earth. That’s because Saturn is almost 10 times farther from the Sun than Earth is. At that distance, the Sun shines only about one percent as bright as it does on Earth. And that presents some problems for spacecraft that travel to Saturn. For one thing, they can’t use solar power. They’d need huge arrays of solar cells, which would make a craft far too heavy and expensive. Instead, Saturn-bound missions are nuclear powered. For another, it’s hard to take good pictures. A craft has to leave the shutter open for a long time to properly expose an image. At the speeds a craft is moving, that blurs the shot. The solution is to turn either the camera or the entire spacecraft to stay focused on the target. No spacecraft are operating at Saturn now. The next one is scheduled for launch in a few years. It’ll ferry a small helicopter to Saturn’s big moon Titan – under the faint light of the distant Sun. Saturn appears near our own Moon early tomorrow. It looks like a bright star, standing just below the Moon at dawn. The planet fades from view as the sky brightens – under the full glory of the nearby Sun. Script by Damond Benningfield

Only about one in five Americans was born before the “Mars Era” – before the first spacecraft visited the Red Planet. That first encounter took place 60 years ago today, beginning six decades of Mars exploration. Mariner 4 was launched in late 1964. A sister craft had failed. And early Soviet efforts failed as well. That inspired jokes about a “great galactic ghoul” eating Mars-bound probes. Mariner 4 had eluded the ghoul for seven months. AUDIO: Then, July 14th: Encounter Day. This is Mariner control. All systems are green. And as this NASA film explained, they stayed green. AUDIO: The shutter is operating, the TV sees the planet, the recorder is working. Mariner skimmed just 6100 miles from Mars. It snapped 21 pictures. The images depicted a landscape of craters and volcanic plains. They made Mars look like a dead planet. Yet Mars exploration continued. Later missions revealed that Mariner 4 was unlucky – it scanned an unusually desolate strip. Today, we know that Mars has an active atmosphere. Ice lurks just below its surface. And it once was warm and wet, with rivers flowing across its surface, perhaps filling a giant ocean – making Mars a possible home for life. Today, a half-dozen orbiters and rovers are exploring the planet. And others are being planned – extending a legacy of exploration that began six decades ago. Script by Damond Benningfield

A brilliant “new” star blazed into view more than a thousand years ago. It’s the brightest star ever recorded, and may be the brightest ever seen by human eyes. Supernova 1006 first appeared in late April of the year 1006. For a few weeks it shined many times brighter than Venus, which is the brightest object in the night sky after the Moon. It was bright enough to see during the day, and remained visible at night for more than two years. It was recorded by cultures around the world. At the time, nobody knew what the star actually was. Today, though, we know it was a supernova. It formed in a binary system. At least one of the two stars was a white dwarf – a stellar corpse. It might have pulled gas from a living companion star. Or perhaps the companion was another white dwarf, and the two stars rammed together. Either way, a white dwarf was pushed beyond its critical weight limit. That caused a runaway nuclear explosion that blasted the star to bits. Debris from the blast continues to race outward at millions of miles per hour. Astronomers watch this debris, mainly in radio waves and X-rays, to learn more about the star and its demise. Supernova 1006 was along the border between the constellations Lupus and Centaurus. The spot is low in the south-southwest at nightfall. But the residue of this brilliant outburst has faded away. Large telescopes reveal only a colorful ribbon at the edge of the expanding bubble. Script by Damond Benningfield

A couple of bright cousins of Antares, the heart of the scorpion, skitter to its lower right on July evenings. They’re the brightest stars of Lupus, the wolf. The stars of Lupus originally formed part of the adjoining constellation Centaurus. But they were split off to form a new constellation a couple of thousand years ago. The wolf’s brightest stars are Alpha and Beta Lupi. Both stars belong to the Scorpius-Centaurus O-B association – a complex of stars and star-making ingredients that spans hundreds of light-years. The first stars in the association were born about 25 million years ago. Beta Lupi probably was one of those stars. Winds from the earliest stars, along with shockwaves from exploding stars, probably triggered a major round of starbirth about five million years later. And two more big rounds followed, spaced about five million years apart. Alpha Lupi probably was born during one of those peaks, no more than 20 million years ago. Alpha Lupi is about 10 times the mass of the Sun. So despite its young age, it’s nearing the end. It will explode as a supernova within the next few million years. Beta Lupi is a little less massive. So it might explode as well. But it’s possible that it faces a less dramatic fate, ending its life as a small, faint ember – a meek end for a mighty star. Lupus is quite low in the south at nightfall. You need to be south of about Dallas or Phoenix to see its brightest stars. More about the wolf tomorrow. Script by Damond Benningfield

Newly forming planetary systems are busy and messy. They contain disks of gas, ice, and dust that are broken into wide bands. The supply of dust is replenished by frequent collisions between “exocomets” – balls of ice and rock up to a few miles across. And the bands may be stirred by the back-and-forth shifting of newborn planets. There’s a similar band in our own solar system – the Kuiper Belt. It begins beyond the edge of Neptune, the outermost major planet, and extends billions of miles from the Sun. Because the solar system has been around for billions of years, the belt is quiet – there are few collisions and little stirring. Astronomers recently studied the bands in about 300 young star systems. They contain a lot of leftover debris from the birth of the planets. So collisions between larger bodies are much more frequent. The impacts blast out a lot of dust, feeding the bands. In many systems, there’s more than one band. Gaps between them might have been cleared out by orbiting planets. And the bands come in different sizes. Wider ones might have been “pumped up” as giant planets moved toward and away from the parent star. The gravity of those planets would have kicked many of the exocomets into different orbits, causing them to spread out. The study didn’t see any planets. But the configurations of the bands suggest the planets are there – taking shape in the busy space around young stars. Script by Damond Benningfield

When it comes to the night sky, what you see isn’t necessarily what you get. Consider Venus and Aldebaran, which are low in the east at first light. Venus is the brilliant “morning star.” Aldebaran stands directly below Venus, and shines just one percent as bright. But their apparent brightness is the only way in which Venus outranks Aldebaran. Venus is a planet in our own solar system – a little smaller and less massive than Earth. It’s so brilliant because it’s close to both Earth and the Sun, and because it’s covered in bright clouds. Aldebaran, on the other hand, is a true star – and an impressive one at that. It’s heavier than the Sun, about 45 times wider, and more than 400 times brighter. Compared to that, Venus is a bare speck – a flake of cosmic jetsam. Aldebaran is almost half a million times more massive and 5,000 times wider – so big that you could pack more than a hundred billion Venuses into its great bulk. So Aldebaran appears fainter than Venus only because of its greater distance – almost four million times farther than the morning star. Look for this mismatched pair beginning a couple of hours before sunrise the next few mornings. Venus will slide to the lower left, and will stand side by side with Aldebaran on Wednesday. They’ll pull apart after that, with Venus dropping a little lower in the sky day by day, and Aldebaran climbing a little higher. Script by Damond Benningfield

Thunderstorms generate what may be nature’s most impressive displays: lightning. And there’s plenty of it; lightning strikes Earth millions of times every day. Although lightning is common, it’s also mysterious. The electric fields inside clouds don’t appear to be strong enough to power lightning. So for the past 90 years, scientists have pondered whether it might have a cosmic origin – cosmic rays – particles that ram into Earth’s atmosphere at almost the speed of light. Many of them come from the Sun. But the most powerful come from exploding stars, the gas around black holes, and other powerful objects in deep space. When a cosmic-ray particle hits an atom or molecule in the upper atmosphere, it creates a shower of other particles. And it’s these particles that might then zip through clouds, creating lightning. A study published earlier this year seems to affirm this idea. Scientists studied a thunderstorm over New Mexico with a sophisticated array of radio antennas. They traced more than 300 strikes from beginning to end, at intervals of less than a thousandth of a second. Among other things, the radio waves revealed that the bolts weren’t moving the way they should if they’d been sparked by the clouds themselves. Instead, the lightning seemed to be triggered by something coming from beyond Earth: cosmic rays. Script by Damond Benningfield

If you throw a rock into a still pond, waves ripple outward. They jiggle the leaves and bugs on the surface, shaking things up a bit. And the same thing happens in the stars. In fact, a giant region of the sky is still feeling some “ripples” today. The Scorpius-Centaurus O-B Association contains many stars of classes O and B – the hottest and brightest stars in the galaxy. It spans hundreds of light-years, and contains thousands of stars. And more stars are being born there today. The association began as a massive cloud of gas and dust. About 20 million years ago, it produced a big “wave” of starbirth. Many of the newborn stars quickly exploded as supernovas. That outburst was the “stone” in the pond. Strong winds and shockwaves from the stars rippled outward. That triggered the birth of more stars in the surrounding cloud. The rate of starbirth peaked about 15 million years ago. But the ripples didn’t stop. They created a smaller outburst about 10 million years ago, and another about five million years ago. Most of the stars in the region are no bigger than the Sun. But a few are big, heavy, and bright – monster stars born from the ripples in a galactic pond. Many of these monsters are in Scorpius, which is low in the south at nightfall, to the right of the Moon. It’s marked by the scorpion’s bright “heart,” the star Antares – the most prominent member of the Scorpius-Centaurus Association. Script by Damond Benningfield

The star that marks the heart of the scorpion is at death’s door. Sometime in the next million years or so, Antares is expected to explode as a supernova. But astronomers don’t know exactly when that’ll happen. There’s no way to see into its core, which is where the fusion reactions that power the star take place. And with current technology, we can’t tell that the end is near by looking at the surface of Antares. The star is many times the mass of the Sun, so when its nuclear engine shuts down, its core will collapse to form a neutron star or black hole. Its outer layers then will blast outward at a good fraction of the speed of light. But the star is so big that the shockwave won’t reach the surface for many hours, so it won’t begin to brighten for hours. The shockwave is powered in part by neutrinos – particles created during the collapse. They almost never interact with other matter, so most of them will zip through the star at almost the speed of light. But there are so many of them that the rare times they do interact will help drive the blast. As the neutrinos race through the galaxy, they’ll reach detectors on Earth hours before the surface of Antares begins to brighten – alerting us to the brilliant demise of a giant star. Antares stands to the upper right of the Moon at nightfall, and leads the Moon down the southwestern sky later on. We’ll have more about the scorpion tomorrow. Script by Damond Benningfield

The Moon will step on the head of the scorpion tonight. It will pass directly in front of one of the stars that outlines the head, blocking it from view – an event called an occultation. Pi Scorpii is actually a system of three stars, about 600 light-years away. The main star in the system is about a dozen times the mass of the Sun, and more than 20,000 times the Sun’s brightness. Because of its great mass, it’s already nearing the end of its life, even though it’s billions of years younger than the Sun. Before long, it will explode as a supernova. The Moon sometimes passes in front of the star because Pi Scorpii lies near the ecliptic – the Sun’s path across the sky. The Moon’s orbit around Earth is tilted a bit, so it roams a few degrees either side of the ecliptic. That allows it to occult quite a few stars that are bright enough to see with the unaided eye. This month alone, in fact, the Moon will stage almost a dozen occultations. But each of them is visible across only a small slice of the globe, so we don’t see all of them from here in the United States. But some of them align just right – allowing us to see the Moon briefly stomp out a star. The occultation of Pi Scorpii will be visible across almost all of the Lower 48 states. The exact time, and how long the star remains blocked, depends on your location. We’ll talk about the Moon and the heart of the scorpion tomorrow. Script by Damond Benningfield

Antimatter may power more than just starships. It might also have helped rev up the BOAT – an exploding star nicknamed “the Brightest Of All Time.” It was seen in October of 2022, in Sagitta, the arrow. Right now, the constellation is in the east at nightfall. The event was a gamma-ray burst – a stellar explosion that aimed “jets” of gamma rays in our direction. It was by far the most powerful cosmic event ever seen. It produced more energy in one second than the Sun will generate in its entire lifetime of more than 10 billion years. It was so powerful, in fact, that it created minor disturbances in Earth’s upper atmosphere – even though it was more than two billion light-years away. The outburst probably happened when a star many times the mass of the Sun died. Its core collapsed to form a black hole, while its outer layers blasted into space as a supernova. As the star died, superheated gas spiraled around the black hole. Magnetic fields directed some of that material into space from the star’s poles. Earth lined up along one of those beams, which is why we saw the outburst of gamma rays. A recent study says that an odd feature recorded during the outburst might have been produced when electrons and their antimatter counterparts rammed together and destroyed each other. That would have added to the energy of the blast – helping make the gamma-ray burst the BOAT – the Brightest of All Time. Script by Damond Benningfield

A giant tarantula creeps through a nearby galaxy. It’s not trying to be stealthy, though – it’s the galaxy’s brightest feature. In fact, it’s the most impressive stellar nursery in the entire Local Group – the cluster of dozens of galaxies that includes the Milky Way. The Tarantula Nebula is in the Large Magellanic Cloud, a companion galaxy to the Milky Way that’s just 160,000 light-years away. Over the last few million years, the nebula has given birth to millions of stars. That’s probably the result of a close encounter with a smaller galaxy. The gravity of the other galaxy caused large clouds of gas and dust to collapse, forming new stars. The Tarantula incorporates several star clusters – groups of stars that all formed at about the same time. The most impressive is R136. It contains a half-million stars, most of which are no more than three million years old. Most of those stars are the mass of the Sun or lighter. But a few are monsters that are many times heavier than the Sun. At least nine of them are more than a hundred times the Sun’s mass. And the biggest of all may be more than two hundred times the Sun’s mass – the heaviest star yet seen in any galaxy, including our own. Within the next few million years, many of these stars are likely to blast themselves to bits as supernovas. In fact, a star on the outskirts of the nebula did just that in 1987 – a brilliant outburst from the tarantula. Script by Damond Benningfield

Fireworks will light up the skies of many cities and towns this week – celebrations of Independence Day. For a real fireworks display, though, you might want to visit one of the Milky Way’s companion galaxies. It’s giving birth to many thousands of new stars, including some of the biggest and brightest yet seen anywhere – a result not of independence, but of a close relationship with another galaxy. The Large Magellanic Cloud is too far south to see from the continental United States. In southern-hemisphere skies, though, it’s quite a sight – a bright cloud that’s several times bigger than the full Moon. The galaxy is much smaller and fainter than the Milky Way. But it’s right next door – just 160,000 light-years away. That’s one of the reasons it looks so bright. Another is that the galaxy contains millions of hot young stars – stars that are thousands of times brighter than the Sun. And it’s giving birth to more. In fact, it contains a stellar nursery that’s far more impressive than anything in the Milky Way. We’ll have more about that tomorrow. The fireworks probably are the result of an interaction with another galaxy, the Small Magellanic Cloud. The smaller galaxy passed close to the bigger one. That encounter squeezed giant clouds of gas and dust. The clouds split into smaller clumps, which gave birth to new stars – creating fireworks in a busy galaxy. Script by Damond Benningfield

The Sun is an impressive star. Its mass ranks in the top 10 percent of all the stars in the galaxy. But the bright star that snuggles up to the Moon the next couple of evenings puts the Sun to shame. It’s bigger and heavier, it has a close companion, and it’s shaped a bit like an egg. And it faces a more dramatic fate. Spica is the brightest star of the constellation Virgo. It consists of two stars – the bright star we see, plus a close companion that we can’t see. We know the companion is there because it reveals its presence to special astronomical instruments. The stars are so close together that their gravitational pull on one another makes both of them look more like eggs than balls. The main star is called Spica A. It’s more than 10 times the mass of the Sun. At that great heft, it gulps its nuclear fuel in a big hurry. That makes the star especially hot and bright – more than 20 thousand times brighter than the Sun. Spica A also is about seven and a half times the Sun’s diameter, and more than 400 times its volume. And its fate is king-sized as well. Within a few million years, it will explode as a supernova – briefly shining as the brightest object in the entire galaxy. Look for Spica to the left or upper left of the Moon this evening. The Moon will slide a bit closer to the star before they set, after midnight. Spica will stand closer to the Moon tomorrow night. Script by Damond Benningfield

When it comes to Earth’s orbit around the Sun, the more things change – well, the more things change. Over the course of a year, our distance from the Sun varies by about three million miles. But that’s changing. And we’re farthest from the Sun in early July – but that’s changing, too. The farthest point from the Sun is known as aphelion – from Greek words that mean “far from the Sun.” And we’ll reach that point on Thursday. Earth will receive about seven percent less sunlight than it does when we’re closest to the Sun, in early January. Earth’s orbit around the Sun is elliptical – like a slightly flattened circle. But the exact shape changes over a period of about a hundred thousand years. Right now, the orbit is getting a little more circular, so there’ll be a smaller change in the distance to the Sun. After that, it’ll get a lot more stretched out. That will cause much bigger changes in Earth’s climate between the closest and farthest points. The timing of those points also changes. About 800 years ago, aphelion happened around the time of the summer solstice in the northern hemisphere. Now, it’s shifted a couple of weeks later. And the shift is continuing. So, about 4400 years from now, aphelion will happen at the fall equinox, in September. It’ll return to its current spot on the calendar more than 20,000 years from now. Tomorrow: A bright star that looks like an egg. Script by Damond Benningfield

Lots of star clusters adorn the evening skies of summer. That’s because the glowing path of the Milky Way climbs high into the sky. It’s the combined glow of millions of stars that outline the disk of the Milky Way Galaxy. So not only does it contain lots of individual stars, it hosts many star clusters as well. But a few clusters are far from the path of the Milky Way. One example is Messier 5. It’s in Serpens Caput – the head of the serpent – a region with not much around it. M5 is a globular cluster – a big ball packed with several hundred thousand stars. Such clusters are scattered all across the sky. Some appear in the disk, but they’re not part of the disk – they loop high above and below it. Globular clusters are the oldest members of the galaxy. And M5 is one of the oldest – 12 billion years or older. That means its original stars were born when the universe was only about one-tenth of its present age. Any stars that were more massive than the Sun have burned out. So the remaining original stars are smaller and fainter than the Sun. There’s evidence that a second wave of starbirth rippled through M5 well after the cluster was formed. Some of these stars can still rival the Sun – the “youngsters” of an ancient star cluster. Messier 5 is high in the south at nightfall. Through binoculars, it looks like a fuzzy star. A small telescope reveals some of the cluster’s individual stars. Script by Damond Benningfield

Mars and the Moon stage a spectacular encounter this evening. The Moon will slide just a fraction of a degree from the planet, which looks like a bright star. Something we’ve learned about both of these worlds is that they have a lot of frozen water. On the Moon, it’s mixed in with the dirt and pebbles, or buried in craters that never see the Sun. On Mars, it’s also mixed in at the surface, but it’s also found in the polar ice caps, in layers of frost, and elsewhere. On Mars, there’s even evidence of liquid water far below the surface. A study last year said there could be a lot of water buried in spaces in the rocks about 10 miles down – enough water to cover the surface of Mars in an ocean about a mile deep. And earlier this year, scientists in Japan reported more evidence of that water. They analyzed the observations of the InSight lander, which operated for four years. The craft listened for “marsquakes.” Sound waves from the quakes traveled through the planet. The new study looked at how different types of waves rippled through the interior. Each type of wave travels differently as it passes through different materials – rock versus water, for example. So comparing the waves revealed the likely presence of water miles below the surface. On Earth, where there’s water, there’s life. So an ocean’s-worth of water could provide a home for life on the Red Planet. Script by Damond Benningfield

The crescent Moon and two bright pinpoints stairstep up the western sky this evening. Regulus, the star that represents the heart of the lion, is to the upper left of the Moon. And the planet Mars is about the same distance to the upper left of Regulus. The trio sets in late evening. The largest feature on the Moon has never been seen directly by human eyes – only by robots. That’s because it’s on the Moon’s far side – the hemisphere that always faces away from us. Only a sliver of its edge can be seen from Earth. And Apollo astronauts saw only a sliver of the opposite edge. South Pole-Aitken Basin is about 1600 miles wide – one of the largest impact features anywhere in the solar system. It probably formed when a giant asteroid slammed into the Moon soon after the Moon was born. A Chinese lander, Chang’e 6, touched down in the basin last June. A few weeks later, it brought about four pounds of rocks and dust to Earth. Analysis of some of the samples confirmed that the basin was gouged four and a quarter billion years ago. But the dark volcanic rock that coats much of the basin formed just 2.8 billion years ago, when an ocean of magma cooled and crystallized. Samples from the near side of the Moon indicate that it was coated with magma at the same time. So the entire lunar surface was covered by an ocean of molten rock – the side we can see, and the side we can’t. Script by Damond Benningfield

Two decades before astronauts walked on the Moon, American movie-goers got a good preview of what the trip might look like. “Destination Moon” was the first big space movie. And it was the first to accurately explain the science and engineering of a trip to the Moon. Co-written by science-fiction author Robert Heinlein, the movie premiered 75 years ago today. In the story, millionaire businessmen decide to finance a lunar voyage. They build a nuclear-powered rocket in the desert, then send it on its way. Problems ensue, but the crew lands on the Moon and makes it back home safely. The backers are convinced in part by a short cartoon that accurately explained how rockets work. In fact, the cartoon was so good that NASA later used a revised version to explain rockets to the public. Destination Moon also showed the effects of acceleration and zero-gravity. During a spacewalk, one of the crew maneuvered using a tank of oxygen; the first real American spacewalker used a similar technique. And on the Moon, the crew loped along just like the Apollo astronauts. The film didn’t get everything right. The landscape – painted by space artist Chesley Bonestell – was too sharp and craggy. And the art director added cracks to the surface like those in a dry riverbed to add a feeling of depth. Still, Destination Moon remains one of the most accurate movies about spaceflight – a fantastic trip to the Moon long before the real thing. Script by Damond Benningfield

Early in its history, the inner solar system was chaotic. Violent collisions might have destroyed many small worlds, while perhaps creating others – including the Moon. It probably formed when a planet as big as Mars rammed into Earth, blasting out debris that came together to make the Moon. A recent study says that a meteorite discovered a few years ago might be a remnant of one of the demolished worlds. NWA 15915 was discovered in Algeria. Scientists analyzed the composition, structure, and magnetic properties of the six-pound meteorite. They concluded that it’s a rare type of meteorite – it doesn’t come from any known asteroid, planet, or moon. But it does have some similarities to Mercury, the smallest planet and the one closest to the Sun. The study suggests that NWA 15915 might have come from a Mercury-like planet born in the same region of the solar system. The planet was demolished long ago by a giant impact. But a few fragments remain. The findings are preliminary. So it’ll take more work to confirm that a piece of a dead planet fell atop the desert sands of northwestern Africa. Mercury itself is near the Moon this evening. It looks like a fairly bright star to the left of the Moon. They’re quite low in the sky as twilight fades, so you need a clear horizon to spot them. Script by Damond Benningfield

It would be fascinating to get close to Cygnus X-3. Unfortunately, it also would be deadly. The system is bathed in X-rays and ultraviolet radiation. It features powerful “jets” that blast into space like energy cannons. And it probably has a black hole – a one-way trip to oblivion. Cygnus X-3 is in the swan, which swoops across the eastern sky on these early summer evenings. The system itself is too faint to see. In fact, we can’t see its visible light even with the largest telescopes because it’s hidden behind thick clouds of dust. But we can see it in other wavelengths, including X-rays, gamma rays, and radio waves. Those forms of energy have allowed astronomers to piece together the system’s likely story. Cygnus X-3 probably consists of a black hole plus a brilliant companion. The companion probably is a dozen or more times the Sun’s mass, and a couple of hundred thousand times its brightness. The bright star is blowing huge amounts of gas into space. The black hole grabs some of the gas, which forms a spinning disk around the black hole. Some of the gas is funneled into high-speed jets that fire into space. One of those jets is aimed almost directly at Earth. The brilliant companion star is likely to explode in the next million years or so, with its core collapsing to form another black hole. But the blast might rip the system apart – perhaps causing Cygnus X-3 to fade away. Script by Damond Benningfield

425 years ago, a “new” star flared to life near the neck of Cygnus, the swan. The star slowly faded, then flared twice more during the 17th century. It’s remained visible ever since. And someday soon, it’ll flare up again – for the last time: It’ll explode as a supernova. P Cygni is more than 5,000 light-years away, so it must be extremely bright for us to see it at all. And in fact, it’s one of the brightest stars in the entire galaxy – 600 thousand times brighter than the Sun. P Cygni is so brilliant because it’s 35 to 40 times the mass of the Sun. Such a monster burns through the nuclear fuel in its core in a hurry. So even though P Cygni is only a few million years old – compared to four and a half billion years for the Sun – it’s nearing its end. The earlier outbursts might have erupted because the star’s interior is unstable. It gets so hot that the star blasts some of the gas at its surface into space. There’s evidence that similar outbursts took place thousands of years earlier. P Cygni is likely to explode within a couple of million years. Its core might collapse to form a super-dense neutron star – or even a black hole. Under dark skies, P Cygni is visible to the eye alone. At nightfall, it’s in the east-northeast, close to the right of Sadr, the bright star that connects the swan’s body to its wings. More about the swan tomorrow. Script by Damond Benningfield

Cygnus, the swan, soars gracefully through summer nights. Its brightest star, Deneb, is in the northeast at nightfall. It marks the swan’s tail. The swan’s body stretches to the right, parallel to the horizon. The wings extend above and below, connected to the body by the star Sadr. Cygnus contains many star clusters. The list includes several that stretch from Sadr to the south, roughly along the swan’s neck. The clusters contain a few dozen to a few hundred stars. All of them are young – no more than about 10 million years old. And many of them are especially hot, bright, and massive. The clusters are indirectly related. They belong to much larger collections of young stars, plus the raw materials for making more stars. A “wave” passed through that region of the galaxy, squeezing gigantic clouds of gas and dust. Clumps of material within the clouds collapsed, forming stars. Over the next few million years, the most massive stars will explode as supernovas. Shockwaves from the blasts may compress more pockets of gas and dust, creating more stars. But the clusters themselves won’t survive much longer – at least on the galactic timescale. They’ll be pulled apart by the gravity of the surrounding stars and clouds, so their stars will go their separate ways. The clusters are easy targets for good binoculars. One is just a whisker from Sadr. Several others trail off to the right – sparkly decorations for the swan. Script by Damond Benningfield

The Royal Observatory at Greenwich has been one of the most important skywatching sites in history – not so much for what it told us about the stars, but for its role right here on Earth. Its location marked the starting point for measuring longitude – the position east and west on the globe. It also marked the time standard for the entire world: Greenwich Mean Time. The observatory was established on today’s date in 1675, by King Charles II. It was built on a hill near London, overlooking the Thames. Greenwich was created to provide highly accurate maps of the stars, and to measure the motions of the Sun, Moon, and planets. The work was designed to help sailors determine their longitude. Establishing longitude at sea was extremely difficult – and dangerous; many ships crashed because their navigators didn’t know where they were. The observations also played a key scientific role: they helped confirm that the motions of the Sun, Moon, and planets were governed by Isaac Newton’s laws of gravity. In 1833, the observatory began a “time service.” It dropped a ball from a tall pole at precisely 1 p.m. That allowed mariners to set their clocks before they sailed. Greenwich later transmitted the time to the whole country by telegraph, then radio. The observatory was moved in the 20th century, and closed in 1998. Today, the Greenwich site is a museum – preserving an important part of world history. Script by Damond Benningfield

The only astronomical object most of us notice in the daytime sky is our star, the Sun. Its light makes the sky bright, which overpowers the other stars and almost everything else. But there are a couple of exceptions: the Moon and the planet Venus. During its 29-and-a-half-day cycle of phases, the Moon spends half of its time in the daytime sky – the hours between sunrise and sunset. But it’s so pale compared to the Sun that it can be hard to notice. That’s especially true when the Moon is in its crescent phase, as it is now. At dawn tomorrow, the Sun will light up only about one-eighth of the lunar hemisphere that faces our way. So the Sun will look millions of times brighter than the Moon. As twilight begins, the Moon will continue to dominate the sky. But as twilight gets brighter, the Moon will appear to fade. It’s still just as bright, but against the daytime sky it’s hard to see. But you can still spot it, leading the Sun across the sky. At dawn, Venus stands to the lower right of the Moon. It’s the brilliant “morning star.” Until sunrise, only the Moon outshines it. Venus also fades into the blue of the daytime sky. But it is visible to the unaided eye. It leads the Moon up the sky in the morning, and down the sky in the afternoon. It’s hard to find, but once you see it, you’ll wonder why you never noticed it before – a bright planet shining through the bright blue sky. Script by Damond Benningfield

The Sun is at a standstill. Oh, it’s still orbiting the center of the galaxy at an impressive clip – about half a million miles per hour. And it’s still moving across the sky as Earth turns on its axis. But the points along the horizon at which the Sun rises and sets aren’t changing. That’s because today is the summer solstice. It’s a point in Earth’s orbit that marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. We have seasons because Earth is tilted on its axis. At the June solstice, the north pole tilts toward the Sun, bringing more sunlight to the northern hemisphere. Six months later, the south pole tilts toward the Sun, giving the northern half of the globe shorter days and longer nights. Between the solstices, the Sun moves north and south in the sky. So its rising and setting points move north and south as well. At some times of year, if you have a good way to mark these points, you can see the difference from day to day. But the Sun appears to “stand still” along the horizon for a few days on either side of the solstice. In fact, the word solstice means “Sun stands still.” At the June solstice, the Sun is farthest north for the year, so it rises and sets to the north of due west. Just how far north depends on your latitude. Incidentally, the summer solstice is also the longest day of the year, so there’s plenty of sunlight as we head into summer. Script by Damond Benningfield

The number of confirmed planets in other star systems has reached about 6,000. But few of those planets are likely homes for life. Most are too hot, too cold, too “gassy,” or they’re zapped by too much radiation by their star. A few planets are in the “well, maybe” category. They might be suitable for life, but the conditions aren’t perfect. An example is a planet in the star system 82 Eridani. The system is about 20 light-years from Earth, and its star is similar to the Sun. Astronomers have confirmed three planets in the system, with hints of more. Two of the planets are quite close to the star, so they’re too hot for life like that on Earth. But the third planet is more intriguing. It’s about six times the mass of Earth, so it could be dense and rocky. Its average distance from the star is about a third farther than Earth’s distance from the Sun. At that range, the planet spends most of its time in the star’s habitable zone – the region where conditions are most comfortable for life. But the planet’s orbit is so lopsided that the distance varies by more than a hundred million miles. So as the planet moves around 82 Eridani, surface temperatures range from hot enough to boil water to cold enough to freeze the entire surface. That makes it unlikely that anything lives on the planet. It is possible that life could exist below the surface – avoiding the extremes on this “yo-yoing” planet. Script by Damond Benningfield

Astronomers have been searching for planets around one of our closest neighbor stars for decades. And they’ve reported the discovery of several. But the reports have come to naught – until now. Earlier this year, a team confirmed the presence of four planets – all of them smaller than Earth. Barnard’s Star is six light-years away. Only the three stars of the Alpha Centauri system are closer. The star is much smaller and less massive than the Sun, and less than one percent as bright. In fact, it’s so faint that it wasn’t discovered until a little more than a century ago. Barnard’s Star is ancient – probably twice the age of the Sun or older. So if it has planets, there’s been plenty of time for life to take hold. That’s made finding planets a high priority. Last year, a team of astronomers confirmed one planet, and said there might be three more. All of those were confirmed in March. None of the planets is more than a third the mass of Earth. And they’re so close in that they orbit the star in a week or less. So even though Barnard’s Star is faint, the planets are all too hot to provide comfortable conditions for life. Barnard’s Star is in Ophiuchus, the serpent-bearer. The constellation stretches across the east and southeast in early evening, and stands high in the south later on. But Barnard’s Star is too faint to see without a telescope. We’ll have more about exoplanets tomorrow. Script by Damond Benningfield

If you stare at one of the giant planets of the outer solar system long enough, with a big enough telescope, you’re likely to find some moons. That was certainly the case a couple of years ago for Saturn. A research team scanned the space near Saturn with a large telescope in Hawaii. And earlier this year, the team reported its results: a haul of 128 previously unseen moons. That brought the planet’s total to 274. That’s three times the number of moons for second-place Jupiter – at least for now. The newly found moons are small and faint – no more than a few miles in diameter. They follow odd orbits, including some that orbit backwards – in the opposite direction from Saturn’s rotation. Some of the moons may be chunks of space rock that were captured by the giant planet’s gravity. Others may be the remains of larger moons that were blasted apart by collisions. About a third of the moons may be the remnants of a single impact. They form a group named Mundilfari for a Norse god related to Saturn. It’s possible the impact took place within the past hundred million years – adding lots of little moons to Saturn’s family. Look for Saturn near our own moon the next couple of mornings. The planet looks like a bright star. It’ll stand to the lower left of the Moon at dawn tomorrow, and closer to the right of the Moon on Thursday. Tomorrow: a passel of planets for a nearby star. Script by Damond Benningfield

If you sit on a big beachball, it gets mashed down. That makes it a little wider through the middle, and a little narrower from top to bottom. And that makes it look a lot like Alderamin, the brightest star of the constellation Cepheus the king. The star is about a third wider through the equator than through the poles. That’s not because some cosmic giant is sitting on it. Instead, it’s because the star spins like crazy. Alderamin is about 50 light-years away, so it’s a fairly close neighbor. It’s nearing the end of the prime phase of life, even though it’s billions of years younger than the Sun. That’s because it’s twice as massive as the Sun. Heavier stars “burn” through their nuclear fuel much faster than lighter stars. What really stands out about Alderamin, though, is its shape. The star’s equator rotates once every 12 hours, versus almost four weeks for the Sun. That forces gas outward around its middle, making the star look a bit more like a fat lozenge than a ball. As Alderamin continues to age, though, it will puff up to many times its current diameter. That will slow down its high-speed rotation, giving Alderamin a “rounder” appearance. Cepheus is in the north and northeast at nightfall. Under fairly dark skies it’s easy to make out. It looks like a child’s drawing of a house. The peak of the roof is on the left during the evening, with Alderamin marking the top right corner of the sideways house. Script by Damond Benningfield

Capricornus may be the most inventive constellation of the zodiac. For one thing, all of its stars are faint, so it takes some work to see any kind of pattern there. And for another, it represents the oddest creature in the heavens: a sea-goat – the front half of a goat plus the tail of a fish. It’s easy to find the sea-goat’s location early tomorrow, because the Moon passes quite close to its brightest star. Unfortunately, the Moon will overpower most of the nearby stars, so you might want binoculars to help you see them. The sea-goat’s leading light is known as Delta Capricorni or Deneb Algedi – the tail of the goat. It’s about 39 light-years away. It’s actually two stars locked in orbit around each other. The main star is twice the size and mass of the Sun, and about eight times the Sun’s brightness. The other star is smaller and fainter than the Sun. Twice a day, Delta Cap fades a bit. That’s because its stars orbit each other once per day. And they’re aligned in such a way that they eclipse one other during each orbit. The system dims a bit more when the faint star passes in front of the bright one, and a bit less when it’s the other way around. The stars of Capricornus form a wide triangle. Delta Cap is at the left point of the triangle. It climbs into good view by about 1 a.m. less than a degree from the bright Moon. Script by Damond Benningfield

A perfect spiral galaxy would include a bright, round “bulge” of stars in the middle; glittering spiral arms wrapping around it; dark lanes of dust lacing through the arms; and bright star clusters sprinkled about like lights on a Christmas wreath. In other words, it would look just like Messier 81, one of the best examples of a “grand design” spiral galaxy. It’s about 12 million light-years away, and appears close to the bowl of the Big Dipper. It’s a bit smaller and less massive than our own home galaxy, the Milky Way. M81’s “bulge,” though, is much larger and brighter than the one in the center of the Milky Way. And the black hole in the galaxy’s heart is almost 20 times as massive as the Milky Way’s. The spiral arms are outlined by the galaxy’s youngest, brightest stars. Over the past 600 million years or so, a major bout of starbirth has brightened the arms. That outburst is the result of gravitational interactions between M81 and two companion galaxies. The encounters compress big clouds of gas and dust. The clouds break into clumps, which then collapse to form stars – stars that make Messier 81 one of the most beautiful galaxies of all. Under clear, dark skies, you can spot M81 with binoculars. Find the Big Dipper, which is high in the north at nightfall. M81 hangs below the bowl at that hour. It looks like an oval smudge of light that’s almost as wide as the Moon. Script by Damond Benningfield